The External SIP Trunk feature allows you to connect third-party telephony providers (e.g., Zadarma) to your AI voice agents. This enables handling inbound and outbound calls using your own SIP infrastructure instead of built-in telephony services.

​
Overview

External SIP Trunks are used when:
  • you already have a telephony provider
  • you want to route calls through your own SIP server
  • you need flexibility in call handling and infrastructure

​
How It Works

  1. A phone number is configured on your SIP provider (e.g., Zadarma)
  2. Calls are forwarded to your system via SIP (URI)
  3. The system processes the call using the assigned AI agent
  4. Responses are returned through the same SIP connection

​
Provider Configuration (Example: Zadarma)

​
1. Open Phone Number Settings

  • Navigate to: Settings → Virtual Phone Number
  • Select your number
Zadarma Config

​
2. Enable External Server (SIP URI)

  • Enable External server (SIP URI)
  • Set the server address in the following format:
<phone_number>@<system_ip>:<port>
Example: 
13478979600@34.200.57.215:5080
Where:
  • 13478979600 — your phone number
  • 34.200.57.215:5080 — your system SIP endpoint

​
System Configuration

​
3. Create External SIP Trunk

  • Navigate to: Phone Numbers → External SIP Trunks
  • Click New External SIP Trunk
SIP Trunk

​
4. Configure Fields

Fill in the following parameters:
  • Phone Number
    Phone number from your provider
  • Termination URI
    SIP endpoint of the provider
    Example: sip.zadarma.com
  • User Name
    SIP login from the provider
  • Password
    SIP password
  • Name
    Internal label (any convenient name)
  • Enabled
    Must be turned on
SIP credentials are provided by your telephony provider.

​
5. Create Trunk

Click Create to save the configuration.

​
Assign SIP Trunk to Agent

You can attach the SIP trunk in two ways:

​
Option 1 — Agent Settings

  • Open the AI agent configuration (‘General’ tab)
  • Click the Phone Number dropdown
  • Choose your External SIP Trunk
SIP Extension Assign

​
Option 2 — Assignment Section

  • Navigate to ‘Phone numbers’ —> ‘External SIP Trunks’ — > Open your External SIP Trunk
  • Assign an agent from the dropdown
SIP Extension Assign

​
Result

Once configured:
  • Incoming calls are routed through your SIP provider
  • Calls are handled by the assigned AI agent
  • Responses are processed in real time

​
Best Practices

  • Ensure SIP credentials are correct
  • Verify that your provider allows external routing
  • Keep the trunk enabled
  • Test the setup with a real call
  • Use clear and descriptive naming for trunks

​
Notes

  • External SIP Trunks require an active SIP provider
  • Incorrect URI or credentials will prevent calls
  • Ensure network/firewall allows SIP traffic

​
Use Cases

  • Connecting Zadarma, Twilio SIP, Asterisk
  • Using custom VoIP infrastructure
  • Enterprise call routing setups
  • Multi-provider telephony environments